In order for high strength, hardness and high density to be achieved in refractory metal parts, they had to be mechanically deformed after sintering. The disadvantages of mechanical deformation are the extra expense and the risk of cracking or otherwise producing a defective part.
U.S. Pat. No. 4,612,162 relates to hot isostatic pressing (HIP) powder metallurgical materials which have been pressed and sintered to closed porosity (about 90 to 91% of theoretical density). The material is hot isostatically pressed to greater than about 97% of the theoretical density. In order to achieve high strength and hardness in the pressed parts, they must still undergo mechanical deformation.